Development of a highly sensitive colloidal gold semiquantitative method for the determination of difenoconazole residues in citrus.

Introduction: Difenoconazole (DIFE) is a common pesticide used in citrus cultivation; excessive intake can cause neurological damage to the organism, and the existing colloidal gold immunochromatographic test strips cannot meet the requirements for the detection of citrus samples. Methods: Difenoconazole test strip was prepared based on the colloidal gold immunochromatographic technique (GICT), and its application in citrus samples was investigated; with colloidal gold (CG) as the probe, the optimization of GICT parameters, and the determination of reaction method, the immunochromatographic test strips for the detection of DIFE in citrus was developed, and the limit of detection (LOD), specificity, accuracy, and stability of the test strips were verified. Results: The results showed that the visual detection limit of the prepared colloidal gold immunochromatographic test strips was 0.2 mg/kg and the quantitative range was 0.06-0.6 mg/kg, and the test strips could specifically identify DIFE and have no cross-reaction with other common triazole pesticides. The detection method established in this study was verified by the GC-MS method, and the detection results achieved good consistency (R2 > 0.98). Conclusion: The test strips developed in this study have good performance and can be used for highly sensitive detection of citrus samples.

Establishment of a Colloidal Gold Immunochromatographic Method for the Detection of Cypermethrin in Tobacco.

In this study, the establishment of a colloidal gold immunochromatographic method for the detection of cypermethrin in tobacco was achieved by using colloidal gold immunochromatography: strong specificity and high sensitivity of cypermethrin semi-antigens and encapsulants were prepared during the study. The best colloidal gold solution was prepared by spectrophotometer and transmission electron microscope screening; the preparation process of gold-labeled antibodies was optimized, and finally the product of colloidal gold rapid detection test strips for cypermethrin was developed. The results of technical parameters and detection indexes showed that the detection limit of cypermethrin in tobacco was 1 mg/kg, and there was no cross-reaction with bifenthrin, cypermethrin, cyfluthrin and phenothrin, and the detection results of 30 tobacco samples were consistent with those of gas chromatography.

Hapten designs based on aldicarb for the development of a colloidal gold immunochromatographic quantitative test strip.

The common carbamate insecticide aldicarb is considered one of the most acutely toxic pesticides. Herein, rational design was used to synthesize two haptens with spacers of different carbon chain lengths. The haptens were then used to immunize mice. The antibodies obtained were evaluated systematically, and a colloidal gold immunochromatographic strip was developed based on an anti-aldicarb monoclonal antibody. The 50% inhibition concentration and linear range of anti-aldicarb monoclonal antibody immunized with Hapten 1 were 0.432 ng/mL and 0.106-1.757 ng/mL, respectively. The cross-reactivities for analogs of aldicarb were all <1%. The limit of detection of the colloidal gold immunochromatographic strip was 30 µg/kg, and the average recoveries of aldicarb ranged from 80.4 to 110.5% in spiked samples. In the analysis of spiked samples, the test strip could accurately identify positive samples detected by the instrumental method in the GB 23200.112-2018 standard but produced some false positives for negative samples. This assay provides a rapid and accurate preliminary screening method for the determination of aldicarb in agricultural products and environments.

Rapid screening of 70 colorants in dyeable foods by using ultra-high-performance liquid chromatography-hybrid quadrupole-Orbitrap mass spectrometry with customized accurate-mass database and mass spectral library.

A rapid screening method of 70 colorants for regulatory control in dyeable foods was established using ultra-high-performance liquid chromatography-hybrid quadrupole-Orbitrap mass spectrometry (UHPLC-Q/Orbitrap MS) with customized accurate-mass database and mass spectral library. A rapid, high-throughput, and simple sample pretreatment condition with low reagent consumption and high recovery was developed on the basis of ultrasound-assisted extraction and dispersion solid-phase extraction. Rapid screening was conducted by comparing the experimentally measured exact mass of the parent and fragment ions, the isotope pattern, and the retention time with the accurate-mass database and by matching the acquired MS/MS spectra against the mass spectral library. The performance of the method was evaluated in terms of linearity, limits of detection, limits of quantitation, recovery, repeatability, reproducibility, and matrix effect. The proposed method was applied for simultaneous analysis of 70 colorants in seven kinds of dyeable foods, and it exhibited great potential for broad, sensitive, and reliable.

Effects of electrolyzed water treatment on pesticide removal and texture quality in fresh-cut cabbage, broccoli, and color pepper.

The effects of alkaline and acidic electrolyzed water (AlEW, AcEW) treatment on the removal of pesticides (phorate, chlorpyrifos, lambda-cyhalothrin, cyfluthrin, procymidone, and chlorothalonil) and texture quality of fresh-cut cabbage, broccoli, and color pepper were investigated. AlEW efficiently removed pesticides from color pepper, whereas AcEW was the optimal treatment for pesticide removal from cabbage and broccoli. AcEW resulted in greater losses of pyrethroid and organophosphates than fungicides, while AlEW was superior for removing fungicides. The best pesticide removal from cabbage (72.28%-91.04%) was achieved by continuous oscillation treatment, while intermittent oscillation for 20 min achieved optimal results for broccoli and color pepper (72.28%-90.11% and 72.24%-88.12%, respectively). No significant deterioration in texture was detected in samples treated with electrolyzed water for 5-25 min. The results suggest that electrolyzed water treatment is effective for removing organophosphate, pyrethroid, and fungicide residues from fresh-cut vegetables while not negatively affecting their texture quality.

Extensive screening of cyclopeptide toxins in mushrooms by ultra-high-performance liquid chromatography coupled with quadrupole-Orbitrap mass spectrometry.

A non-target screening method of cyclopeptide toxins and their analogues in mushroom was developed, using ultra-high-performance liquid chromatography coupled with quadrupole Orbitrap mass spectrometry (UHPLC-Q-Orbitrap MS) followed by mass spectrometry databases retrieval and software tools analysis for the candidate analogues. Three cyclopeptide toxins in the toxic mushroom Amanita rimosa were firstly screened without standard, and two of them were unknown analogues which were tentatively identified by the accurate masses, isotopic patterns and characteristic fragments. A validated quantitative method was performed to rapidly quantify three major cyclopeptide toxins in the Amanita rimosa sample including α-manitin, ß-amanitin and phalloidin, and their contents were detected to be 4.52 mg/kg, 2.37 mg/kg and 2.53 mg/kg, respectively. The developed method has good selectivity and sensitivity for rapid and comprehensive screening the cyclopeptide toxins and their analogues in mushrooms at trace levels. Successful non-target screening of trace cyclopeptide toxin analogues will guarantee the food safety in mushrooms consumption.

The Epidemiology of Monophasic Salmonella Typhimurium.

Salmonella enterica remains an important foodborne pathogen in all regions of the world, with Typhimurium as one of the most frequent serotypes causing foodborne disease. However, the past two decades have seen a rapid worldwide emergence of a new Salmonella serotype, namely monophasic variant of S. Typhimurium, whose antigenic formula is 1,4,[5],12:i:-. It has become one of the 2-5 most common Salmonella serotypes responsible for animal and human infections in different regions. The global epidemic of monophasic S. 1,4,[5],12:i:- has mainly been characterized by an increase in multidrug-resistant S. 1,4,[5],12:i:- isolated in Europe since 1997. The unexpected link to swine has escalated monophasic S. Typhimurium infections to the status of a global public health emergency. The large-scale application of whole genome sequencing (WGS) in the last 10 years has revealed the phylogenetic associations of the bacterium and its antimicrobial resistance (AMR) genes. Local and global transmission reconstructed by WGS have shown that different clones have emerged following multiple independent events worldwide, and have elucidated the role of this zoonotic pathogen in the spread of AMR. This article discusses our current knowledge of the global ecology, epidemiology, transmission, bacterial adaptation, and evolution of this emerging Salmonella serotype.

Rapid detection of trace Salmonella in milk and chicken by immunomagnetic separation in combination with a chemiluminescence microparticle immunoassay.

Rapid detection of trace Salmonella is urgently needed to ensure food safety. We present an innovative pretreatment strategy, based on a two-step enrichment culture and immunomagnetic separation, combined with a chemiluminescence microparticle immunoassay to detect at least one proliferative Salmonella cell in 25 mL (25 g) food. The capture performance of immunomagnetic beads (IMBs) of sizes for Salmonella was investigated, and the IMBs of size 2.8 µm showed a high capture efficiency of 60.7% in 25 mL milk and 74.5% in 25 mL chicken culture filtrate, which ensured the successful capture of trace Salmonella after 2.5 h in situ enrichment even from only one Salmonella cell. The separated Salmonella cells, reaching an amount of 103 colony-forming units (CFU) by a secondary enrichment for 3 h, were detected by a horseradish peroxidase chemiluminescence reaction with 4-(1-imidazolyl)phenol as an enhancer, which evidenced a linear response for Salmonella concentrations ranging from 2.3 × 102 to 7.8 × 104 CFU/mL. The entire detection process was completed within 8 h, with a very low detection limit of 1 CFU/25 mL (25 g), which was verified by colony counting, and a small degree of interference of 0.17-1.06%. Trace Salmonella from five different serovars in milk and chicken was successfully detected without false negative or false positive results. Furthermore, this study provides a basis to develop a fully automated instrument based on IMBs that includes all steps from sample preparation to chemiluminescence microparticle immunoassay for high-throughput screening of foodborne pathogens. Graphical abstract.

Detection of plasmid-mediated tigecycline-resistant gene tet(X4) in Escherichia coli from pork, Sichuan and Shandong Provinces, China, February 2019.

The plasmid-mediated high-level tigecycline resistance gene, tet(X4), was detected in seven Escherichia coli isolates from pork in two Chinese provinces. Two isolates belonged to the epidemic spreading sequence type ST101. Tet(X4) was adjacent to ISVsa3 and concurrent with floR in all seven isolates. In addition to IncFIB, the replicon IncFII was found to be linked to tet(X4). This report follows a recent detection of tet(X3)/(X4) in E. coli from animals and humans in China.

Microbial composition of spoiled industrial-scale Sichuan paocai and characteristics of the microorganisms responsible for paocai spoilage.

The microorganisms of spoiled industrial-scale Sichuan paocai (ISSP) were isolated using six types of media, and 16S rRNA and 26S rRNA gene sequence analyses were used to identify the isolates. Meanwhile, the microbial composition was investigated using a culture-independent method through 16S rRNA and ITS sequencing on an Illumina MiSeq platform. The results obtained by these two methods were compared. Furthermore, characteristics of the isolated microorganisms responsible for ISSP spoilage were studied. Sixty-two strains belonging to twenty-three species, including three ammonia-producing genera, two gas-producing genera, two pectinase-producing genera, two cellulase-producing genera, three film-producing genera and one slime-producing genus, were isolated. Lactobacillus, Bacillus, Debaryomyces and Kazachstania were the dominant genera as confirmed through both culture-dependent and culture-independent methods. Bacillus, Paenibacillus, Pichia and Debaryomyces could be the main microorganisms responsible for ISSP spoilage. Bac. licheniformis was closely correlated with the off-flavour of ISSP. Pae. peoriae, Bac. stratosphericus, Bac. toyonensis and Bac. cereus were responsible for tissue softening, and Bac. subtilis, Bac. methylotrophicus, Pic. membranifaciens and Deb. hansenii caused film formation.